Several methods are known for demonstrating spectacle lenses or for assessing the properties of spectacle lenses. For demonstrating the optical properties of spectacle lenses, representations of isometric lines or pseudo-3D representations of various optical properties of spectacle lenses are frequently used, for example the surface astigmatism or total astigmatism, the surface power or power, and also the appearance. These representations are of a technical nature and can be interpreted only by a person skilled in the art such as, for example, an ophthalmologist.
EP 1 018 691 A1 describes a method and an apparatus for simulating a visual impression. The method described in this publication permits a potential purchaser of spectacle lenses to judge how he will be able to see with the prospective spectacle lenses. An assessment of his own appearance when using these spectacle lenses is not possible with these known methods.
As a rule, the enormous technical complexity of the product “spectacles”, i.e. of a certain spectacle frame selected by the future user, and the spectacle lenses selected by the user or recommended to him, can be understood only to a limited extent by a spectacles wearer.
The choosing of the spectacle frame normally presents no great problems to the spectacles wearer, because the spectacles wearer is able to see immediately whether a frame suits him or not. Moreover, various aids are available for choosing a frame. Thus it is known, for example, to take a picture of the customer wearing various spectacle frames, so that the customer can choose the spectacle frame most suitable for him by comparing the photographs or video recordings. This manner of proceeding is particularly preferred by strongly ametropic customers, because they are unable to see themselves with the new frame clearly in a mirror.
The disadvantage of all demonstration means that have hitherto been on the market is that only various spectacle frames can be assessed, but not the effect which the spectacle lenses fitted into the spectacle frames have on the appearance of the face of the customer. Stated precisely, the known demonstration means permit only an assessment of optical properties, for example the refractive error or astigmatism of the spectacle lens, i.e. of what the spectacles wearer himself is able to see, but not of the appearance of the spectacles wearer, that is, how the spectacles wearer would be perceived by other persons.
However, the quality of a spectacle lens also and not lastly resides in how a spectacles wearer will appear to an opposite person. If spectacles which magnify too strongly because of a too strongly chosen curvature (basis curve) are worn, a so-called “bulging-eyes effect” will appear. A face is changed when spectacles are worn which, because of a too small curvature (mean curvature of the front surface of the spectacle lenses), show large-area reflection-images or small reflection-images. Furthermore, the face is changed when spectacles are worn which, because of unsuitable anti-reflective properties, show ugly residual reflection colors, or which, because of suitable anti-reflective properties, exhibit aesthetic residual reflection colors.
In order that the customer may be able to choose spectacles optimally, consideration must be given to the spectacle frame as well as to the spectacle lens to be fitted in the spectacle frame.